U.S. patent number 10,670,737 [Application Number 15/742,897] was granted by the patent office on 2020-06-02 for mobile tof-pet insert.
This patent grant is currently assigned to UNIWERSYTET JAGIELLONSKI. The grantee listed for this patent is UNIWERSYTET JAGIELLONSKI. Invention is credited to Bartosz Glowacz, Pawel Moskal, Marcin Zielinski.
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United States Patent |
10,670,737 |
Glowacz , et al. |
June 2, 2020 |
Mobile TOF-PET insert
Abstract
A Time-of-Flight Positron Emission Tomography (TOF-PET)
tomography insert. The insert includes detection modules and
photoelectric converters. Each of the photoelectric converters is
connected to an electronic signal processing circuit protected by a
housing and comprising an electronic signal processing unit and a
computer operable to control the electronic signal processing unit
and to reconstruct and store images. Each of the detection modules
further includes a liquid marker visible in a magnetic resonance
image. The insert also includes a liquid marker device visible in
the magnetic resonance image. Adjacent detection modules are
detachably connected via coupling elements.
Inventors: |
Glowacz; Bartosz (Zory,
PL), Moskal; Pawel (Czulowek, PL),
Zielinski; Marcin (Cracow, PL) |
Applicant: |
Name |
City |
State |
Country |
Type |
UNIWERSYTET JAGIELLONSKI |
Cracow |
N/A |
PL |
|
|
Assignee: |
UNIWERSYTET JAGIELLONSKI
(Krakow, PL)
|
Family
ID: |
56802646 |
Appl.
No.: |
15/742,897 |
Filed: |
July 15, 2016 |
PCT
Filed: |
July 15, 2016 |
PCT No.: |
PCT/PL2016/000082 |
371(c)(1),(2),(4) Date: |
January 09, 2018 |
PCT
Pub. No.: |
WO2017/010896 |
PCT
Pub. Date: |
January 19, 2017 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20180356536 A1 |
Dec 13, 2018 |
|
Foreign Application Priority Data
|
|
|
|
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Jul 16, 2015 [PL] |
|
|
P.413150 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01T
1/1603 (20130101); G01T 1/2985 (20130101); A61B
6/037 (20130101); A61B 5/0035 (20130101) |
Current International
Class: |
G01T
1/16 (20060101); G01T 1/29 (20060101); A61B
5/00 (20060101); A61B 6/03 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
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WO-2015028598 |
|
Mar 2015 |
|
WO |
|
Primary Examiner: Rozanski; Michael T
Attorney, Agent or Firm: Friedman; Mark M.
Claims
The invention claimed is:
1. A Time-of-Flight Positron Emission Tomography (TOF-PET)
tomography insert, comprising: detection modules, each detection
module made of a non-magnetic material and comprising a
scintillator stripe; photoelectric converters, each photoelectric
converter connected to a dedicated scintillator stripe and
configured to convert light signals from the scintillator stripe to
electric signals; wherein each of the photoelectric converters is
connected to an electronic signal processing circuit protected by a
housing and comprising an electronic signal processing unit and a
computer operable to control the electronic signal processing unit
and to reconstruct and store images; wherein each of the detection
modules further comprises, at each of ends of the scintillator
stripe, a liquid marker visible in a magnetic resonance image; a
liquid marker device visible in the magnetic resonance image;
wherein adjacent detection modules are detachably connected via
coupling elements.
2. The tomography insert according to the claim 1, wherein the
adjacent detection modules are detachably connected by a groove and
protrusion coupling.
3. The tomography insert according to claim 1, further comprising a
protective layer made of a non-magnetic material that protects the
detection modules from the inside of a working space formed by the
coupled detection modules.
4. The tomography insert according to claim 1, wherein the
photoelectric converters are silicon photomultipliers arranged in a
two-dimensional matrix comprising at least two elements.
5. The tomography insert according to claim 1, wherein the liquid
marker device is located on a front face of the tomography insert,
the front face being perpendicular to the scintillator stripes.
6. The tomography insert according to claim 1, wherein the liquid
marker device is an ampoule comprising an aqueous solution of a
chemical compound that shortens a longitudinal relaxation time of
water.
7. The tomography insert according to claim 1, Wherein the liquid
markers have a form of ampoules with an aqueous solution of a
chemical compound that shortens a longitudinal relaxation time of
water.
8. The tomography insert according to claim 1, further comprising
at least one bracket.
9. The tomography insert according to claim 8, wherein the bracket
has an output slot for the electronic signal processing circuit
placed at an end of each detection module.
10. The tomography insert according to claim 1, further comprising
a support base made of a non-magnetic material.
11. The tomography insert according to claim 1, comprising a
bracket attached to a support base.
Description
This application claims priority from PCT application No.
PCT/PL2016/000082 filed Jul. 15, 2016 which claims priority from
foreign application No. P.413150 filed Jul. 16, 2015, the
disclosures of which are incorporated by reference.
The present invention relates to the mobile Time-of-Flight Positron
Emission Tomography (TOF-PET) insert for the Magnetic Resonance
Imaging (MRI) scanner which enables simultaneous imaging with PET
and MRI techniques.
Access to anatomical and functional information of the body
interior is possible using, for instance, various tomographic
techniques which are based on the registration of radiation emitted
from the area of tissues and processing collected data into
anatomical image or information about the changes of
physico-chemical properties occurring in studied area.
One of the techniques is Positron Emission Tomography (PET), which
relies on the determination of the spatial distribution of chosen
substance in the body and allows for tracking its concentration
changes in time, thus allowing to determine the rate of metabolism
of the individual tissue cells.
The selected substance is a radiopharmaceutical which is
administered to the patient shortly before performing PET
examination. The radiopharmaceutical, also called isotope label, is
a chemical substance in which at least one atom is replaced by a
radioactive isotope, for example: carbon, .sup.11C, the oxygen
.sup.15O, nitrogen .sup.13N, fluoride .sup.18F, which is chosen to
undergo a radioactive decay with emission of the positron
(anti-electron). Positron is emitted from the nucleus of the
isotope and penetrates into the tissue of the patient, where it
annihilates with electron--present in the patient's body.
Annihilation process of the positron and electron, underlies the
imaging PET technique, where the whole particles masses (electron
and proton) are changed into energy, which is emitted as two
annihilation photons, each with an energy of 511 keV. According to
the momentum conservation principle the two photons propagate in
opposite directions at an angle of 180 degrees in the rest frame of
the positron and electron. The trajectories of the photons form a
straight line which is called Line of Response (LOR). The stream of
many annihilation photons generated in the described process is
called a gamma radiation, and each photon is called the gamma
quantum. The resulting gamma quanta are capable of penetrating
matter--including the tissue of living organisms--which allows to
detect them at certain distance from the patient. The process of
annihilation of the positron and electron is usually within a few
millimeters from the decay point of the radiolabel isotope. This
fact constitutes a natural limitation of PET image accuracy at the
level of a few millimeters.
The PET scanner includes devices that detect gamma radiation,
electronics and software for specifying the location of the
positron-electron annihilation position in the body, based on the
information about the time and place of each of the two gamma
quanta detection. Radiation detectors are commonly arranged in a
form of single layer ring around the patient which consists of
inorganic scintillator material. When the gamma quantum enters the
scintillator material, it absorbs its energy, and then emits it in
the form of light (photon flux). The mechanism of energy absorption
of gamma rays by the scintillator may occur predominantly in two
ways: through Compton or by photoelectric effects, however in the
state of the art PET scanners for the purposes of calculation one
takes into account only the photoelectric effect. Thus, it is
assumed that the number of photons generated in the scintillator
material is proportional to the energy of gamma quantum deposited
in the scintillator. When two annihilation quanta will be
registered by a pair of detectors within few nanosecond time
interval, so-called coincidence window, one can locate the point of
annihilation, lying on the line of the response LOR--which is the
line connecting the center of detectors, or between points in
scintillators stripe in which the gamma quanta deposited its
energy. Coordinates of the annihilation point are obtained based on
the time difference between the arrivals of gamma quanta to the
detectors lying on the two ends of the LOR. In the literature, this
technique is called the Time Of Flight (TOF) method, and PET
scanners exploiting the signals time differences are called
respectively TOF-PET scanners. To use this technique time resolving
accuracy of several hundred picoseconds is required, for the
scintillators detectors.
The state of the art PET scanners are large-size standalone
devices. The cost of such device is very high, in the order of
several million dollars.
To take full advantage of diagnostic information obtained with PET
imaging technique, one should superimpose the map of the spatial
distribution of the radiopharmaceutical administered to the
patient, and the anatomical image of the investigated region of its
body. Anatomical image can be obtained with other tomographic
techniques such as Magnetic Resonance Imaging (MRI). The MRI
tomography uses magnetic properties of atomic nuclei, in particular
hydrogen atoms nuclei, composed of only one proton, widely
occurring in matter, common in the tissues of living organisms, in
a form of water molecule. The MRI technique allows to determine the
density distribution of hydrogen atoms, which then is processed
into morphological image of tissues.
Known MRI scanners are large size standalone devices, with the
production cost in the order of several million dollars.
By superimposing the functional-PET, and morphological MR images
one can significantly increase the diagnostic capabilities, as the
PET image allows for precise determination of location and rate of
metabolic changes, while at the same time the MR image allows to
associate them with the individual organs. Thus nowadays, the PET
and MR simultaneous imaging is intensively developed.
In the state of the art there are already known devices that
combine the PET and the MRI scanners, so-called hybrid PET-MRI
scanners. In the case of simultaneous operation of the two devices
PET and MRI, it is necessary to overcome a number of technological
obstacles. One of the problems is a strong constant magnetic field
and strong electromagnetic pulses used in MRI, which disturb the
operation of commonly used photomultiplier tubes and electronics
for the processing of the signals registered by the PET detectors.
In turn, the solutions currently used in PET systems may affect the
uniformity of the local magnetic field, and disturb the operation
of receiving coils which detects weak electromagnetic fields in the
area of the examined tissue. This is due to the eddy currents and
electromagnetic waves induced in the electronic circuits of PET
scanner.
From the US patent document US 20060052685 A1, a solution is known
based on a system of two independent and spatially separated PET
and MRI devices, between which patient is displaced on a movable
bed, common for both modalities. Although such an arrangement
avoids the problem of mutual interference between the two systems,
it does not ensure the simultaneity of both functional and
anatomical imaging, and also is not performed in the same place.
This creates a high risk of displacement of one image with respect
to the other. Images of organs of the abdominal cavity are the most
vulnerable to the artefacts, as the organs may move and change
their shape, as a result of experienced acceleration during patient
transport between scanners or, as previously mentioned,
physiological movements.
A similar solution, in which the PET and MRI scanners are spatially
separated and positioned in close proximity to each other, is
reported in U.S. Pat. No. 8,013,607.
U.S. Patent Application No. 20130006091 A1, reveals an invention in
which the PET detector is located directly outside the tunnel of
MRI scanner, configured in a way to permit the change of its
geometry size to be adjusted to the size of imaged object and
provide undisturbed movement of the patient into the bore of the
MRI scanner. In this method, the object is firstly subjected to the
MR scan and later the PET imaging is performed, which requires to
displace the diagnosed object into the field of view of the PET
detector, located outside the tunnel of MRI scanner. Described
method reduces the probability of image artifacts occurrence
associated with the movement of the investigated object, only to a
certain extent. Another problem is the time required for the object
to be moved between two systems, folding and unfolding the PET
detector, as well as the repeatability of this operation, which may
influence the geometric relations between the detection modules,
and thus the image reconstruction. It is also important, what was
reported in the cited patent application, that for MR imaging the
transceiver coil designed for the whole body has to be used. This
coil surrounds the MRI scanner tunnel. In the MRI technique, it is
common to use coils for imaging of specific areas of the body, so
the investigated object fills as much as possible the volume
limited by the coil construction. One describes this property by
so-called filling factor parameter, which value determines the
strength of the resonant signal which may be detected from the
object inside the coil. The use of the whole-body coil for the head
imaging substantially limits the amplitude of the recorded resonant
signal, because of the large disparity between the volume enclosed
by the coil and the MRI cylinder diameter (typically 60-70 cm), and
the volume of the head (diameter typically 15-20 cm). For example,
a typical transceiver coil dedicated to study head has about 26 cm
internal diameter. The signal recorded by a resonant coil, adapted
for whole body imaging, may then be 5 to 10 times weaker than that
recorded using a head coil (coils for imaging the head) assuming
the same volume of the test object.
In the present state of technique, as described in U.S. Patent No.
20070102641 A1, the PET detector is also known, arranged along the
tunnel of MRI scanner. Indeed, this solution allows simultaneous
recording of images with the two methods. However the PET detector,
covers only about 25 cm long cylindrical volume in which the
patient is placed. Because of this fact it is inevitable to move
the patient, but this time within one device, at the time of
imaging of the whole body or its larger parts. Typically, the
patient is moved by a distance equal to a half the width of the PET
detector ring, so that recorded images can be then combined
together relying on the repetitive parts of subsequent
acquisitions. The patient 180 cm tall requires, therefore, about 17
independent PET scans between which his body is being moved
together with the scanner bed. Superimposing images increases the
systematic uncertainty during the reconstruction process. In
addition, a significant drawback is a decrease with time in the
activity of a radioisotope administered to the patient, which in
consequence forces correction to the computed data recorded in the
later time of the imaging process.
From the Polish patent application no. P. 405184, a hybrid
TOF-PET/MRI tomograph is known, comprising a TOF-PET and MRI
tomographs, characterized in that the TOF-PET tomograph comprises a
plastic scintillator bars arranged circumferentially inside the
working magnetic field of a transceiver coil of the MRI scanner,
and photo-electric converters of light signals from the
scintillator stripes to electrical signals, and the photoelectric
converters are outside the working area of the magnetic field of
the MRI scanner. In the described solution the embodiment of the
hybrid TOP-PET/MRI tomograph, allows simultaneous PET and MR
imaging, but does not allow to use for this imaging systems which
are used in the traditional MR. The second obstacle and limitation
of this technology is the placement of photoelectric converters
outside the working area of the MRI magnetic field. This requires
the use of long stripes of plastic scintillator elements or optical
fibers which allow to guide the light signal out of the MRI
magnetic field area. Longer optical path to the photoelectric
converters limits the flux of light reaching these converters.
Presented solution can be used only in the production of new hybrid
TOF-MRI scanners. However it cannot be applied to existing MRI
devices.
Presently used PET-MRI hybrid tomographs are bulky standalone
devices, production cost of which is very high.
The obtained hybrid PET/MRI images may be used in research on the
physiological processes where it is essential to accurately
associate the appropriate changes in the tissue with the metabolism
of a radiopharmaceutical at the time of imaging.
The U.S. Pat. No. 7,218,112 presents solution with the use of
silicon photomultipliers. The described method enables simultaneous
imaging in the relatively large transverse field of view. In this
solution, PET detectors are between the transmitting-receiving
coils surrounding the patient and gradient coils. The PET detectors
are composed of lutetium oxyortosilicon crystals (LSO), connected
optically to the matrix of avalanche photodiodes, with integrated
cooling system and the analog readout electronics. Detection
modules are enclosed in copper shields. However, such placement of
PET tomograph in the tunnel of MRI scanner, can lead to the
disturbances of magnetic fields, and electromagnetic signals used
in MRI, and distortion of signals of PET tomograph. The main
factors causing the described disruptions are: converters,
electronic circuits, cooling systems, which are placed between
embodiment of the transmitting-receiving coil and the gradient
coil, the transmission of electric signals between PET detectors
and the transmitting-receiving coils and gradient coil, scattering
of annihilation quantum in the MRI transmitting-receiving coils,
which are placed between the patient and the PET detector
layer.
However, in the case of hybrid systems, still unsolved the problem
remains of use of the coils designed to examine specific parts of
the body, e.g. head or limb. Use of the head coil is technically
possible, but the construction elements of such coil made of
plastic and metal conductors, are placed on the way of the gamma
quantum flight path to the PET detectors, originating from the
annihilation of the positron and electron in the examined volume.
This fact limits the field of view of the PET detectors (so-called
acceptance), and in addition can cause gamma quantum scattering,
thus negatively affect spatial resolving power of PET imaging.
Therefore, it would be favorable to construct a device for imaging
using low-cost plastic scintillators, which would allow
simultaneous recording of gamma radiation and magnetic resonance
imaging with a wide field of view, giving the ability to eliminate
artifacts which may distort the picture due to the movement of the
object, and the systematic uncertainties, that arise in the process
of superimposing the images taken in different places and at
different times. This would allow for an effective functional and
morphological imaging at the same time.
The subject of present invention is to provide a TOF-PET insert,
which will be a TOF device for imaging with PET technology, which
can be placed inside any transceiver coil of existing MRI scanners,
and after placement of such insert inside the transceiver coil of
the MRI scanner, it would be possible to make simultaneous TOF-PET
and MRI imaging, without interrupting the operation of TOF-PET and
MRI scanners. The mechanical construction of the TOF-PET insert
should make possible adjusting the size of the insert to the
dimensions and shape of various types of existing
transmitting-receiving coils of existing MRI scanners, both which
are permanently built-in to the MRI scanner enclosure, and local
coils dedicated to perform studies of individual parts of the
patient body.
A TOF-PET tomography insert, according to the invention, is
comprised of detection modules, each detection module comprising a
scintillator stripe connected, at each end, to a photoelectric
converter to convert light signals from the scintillator stripe to
electric signals, and further connected to an electronic signal
processing circuit protected by a housing, equipped with an
electronic signal processing unit and with a computer having a
software for steering the electronic signal processing unit, and a
software for reconstruction and preserving the image, and is
characterised in that the detection modules are made entirely of
non-magnetic material, and that each detection module is equipped,
at each end, with a liquid marker, wherein the tomography TOF-PET
insert is equipped with a liquid marker device, and each detection
module is equipped with coupling elements for detachable connection
of adjacent detection modules. It is preferable, when the coupling
element constitutes a protrusion, that is located on a cover of a
single detection module, and a groove placed on an adjacent
detection module.
It is preferable, when TOF-PET tomography insert has a protective
layer, made of non-magnetic material to protect the detection
modules from inside of a working space formed by the detection
modules, after coupling thereof.
It is preferable, when the photoelectric converters are silicon
photomultipliers arranged in a two-dimensional matrix, having at
least two elements.
It is preferable, when the liquid marker device is located on the
front face of the tomography insert, perpendicular to the
scintillator stripes.
It is preferable, when the liquid marker device constitutes an
ampoule with an aqueous solution of a chemical compound, shortening
the longitudinal relaxation time of water.
It is preferable, when the liquid markers placed at the ends of the
detection modules, have the form of ampoules with an aqueous
solution of a chemical compound, shortening the longitudinal
relaxation time of water.
It is preferable, when the TOF-PET tomography insert has a
triggering unit.
It is preferable, when the TOF-PET tomography insert is equipped
with at least one bracket.
It is preferable, when the bracket is equipped with an output slot
for the electronic signal processing circuit, placed at the end of
each detection module.
It is preferable, when the TOF-PET tomography insert is equipped
with a support base made of non-magnetic material.
It is preferable, when the TOF-PET tomography insert is equipped
with a bracket and a support base, in such a way that the bracket
is attached to the support base.
The examples of possible embodiment of the invention have been
shown on the drawing, in which FIG. 1 presents schematically a
front view of a TOF-PET tomography insert, FIG. 2 presents
schematically a top view of a detection module, FIG. 3 presents
schematically a perspective view of separated components located at
the end of the detection module, FIG. 4 presents an arrangement of
a few detection modules connected to each other, FIG. 5 presents
the arrangement of the detection modules constituting a workspace
with a shape similar to a cuboid with the hexagon base, FIG. 6
presents schematically a cross-section of the MRI scanner with the
TOF-PET tomograph insert placed inside, whereas FIG. 7 presents a
perspective view of the MRI scanner and the TOF-PET tomography
insert which is placed inside the transmitter-receiver coil
situated on the patient bed of the MRI scanner, before the bed is
inserted into the diagnostic tunnel of the MRI scanner.
As shown in FIG. 4, FIG. 5 and FIG. 7 the TOF-PET tomography insert
1, according to the possible embodiment of the invention, is
comprised of detection modules 2. As shown in FIG. 2 and FIG. 3
each detection module 2 comprises a scintillator stripe 3, which at
both ends is connected to the photoelectric converter 4 which
converts light signals from the scintillator stripe 3 into electric
signals, and further with the signal processing electronic circuit
19, protected with the housing 6.
As shown in FIG. 3, in this possible embodiment of the invention,
the photoelectric converters 4 constitute silicon photomultipliers
17, arranged in a two dimensional array configuration. The size and
dimensions of the silicon photomultipliers 17 array is adapted to
the size and dimensions of the cross-section of the plastic
scintillator stripe 3. If the dimensions of the cross-section of
the stripe are, for example, 5 mm by 20 mm, and the silicon
photomultiplier 17 has dimensions of 5 mm by 5 mm, then four
silicon photomultipliers 17 can be attached to one end of the
scintillator stripe 3. Each silicon photomultiplier 17 is arranged
next to another identical silicon photomultiplier 17, so they
adjoin to each other with the edges. FIG. 3 shows photoelectric
converter 4 composed of silicon photomultipliers 17, arranged in
two columns of five silicon photomultipliers 17 in one column. It
is clear that in other possible embodiments of the invention, one
may use any of known photoelectric converters 4, for example,
avalanche diodes, or photomultiplier tubes. Although the
photoelectric converters 4 are in the magnetic field of the MRI
scanner 20, the tomography TOF-PET insert does not interfere with
the technical parameters of the MRI scanner 20, and does not
interfere the operation of the MRI scanner 20.
Each detection module 2 is equipped with coupling elements for
establishing a detachable connection of detection modules 2,
located next to each other. In this possible embodiment of the
invention, a coupling element constitutes a protrusion 10, located
on the housing 6 of one of the detection module 2, and the groove
11, which is located on the housing 6 of adjacent detection module
2, but it is obvious that other known solutions for detection
modules 2 coupling may be used. Housings 6, through the coupling
elements (protrusions 10 and grooves 11), are rigidly connecting
the two detection modules 2 on both sides. Coupling elements have
the ability to adjust the angle at which they are connected to the
next detection module 2, giving the possibility to choose the
geometry of the entire TOF-PET tomography insert 1.
Detection modules 2 may be connected together in such a way that
they constitute a workspace 14 of the TOF-PET insert in the form of
a cylinder, as shown in FIG. 1, FIG. 6 and FIG. 7, or with a shape
similar to a cuboid with the hexagon base, as shown in FIG. 5, or
any other. Detection modules 2 may consist of the plastic
scintillator stripe 3, of arbitrary length and cross-section shape.
It is not possible to change the physical properties of already
made plastic scintillator stripes 3, but geometries and sizes may
be chosen during the plastic scintillator stripes 3 manufacturing
process to adapt the plastic scintillator stripe 3 to the specific
application or geometry of investigated object.
With the use of many stripes of different shapes, depending on the
requirements, one may assemble the tomography TOF-PET insert in
such a way that it will fit to a specific transmitter-receiver coil
22, such as a head coil of a specific MRI scanner 20. The variable
connection angle on the coupling elements between the detection
modules 2, allows for changing the configuration of the detection
modules. The number of detection units 2 can be chosen to adjust
the size of the TOF-PET tomography insert to actual needs: removing
or adding individual detection modules 2 to the configuration. The
imaged volume of the patient's body 5, depending on what structures
it concerns, can be put into the interior of the TOF-PET tomography
insert (head, upper/lower limb, for instance) or two halves (top
and down) of the TOF-PET tomography insert may be imposed one to
another surrounding the investigated volume of the patient's body 5
(chest, for example).
To strengthen the construction formed from the detection modules 2,
bracket 16 may be applied, which has sockets for the outputs 18,
outgoing from the signal processing electronic circuit 19 at the
ends of the detection modules 2. In the possible embodiment, shown
in FIG. 5, two brackets 16 were utilized on both sides of coupled
detection modules 2. Brackets 16 at the same time support and
protect power and signal circuits, supplied to the detection module
2 at each side. The bracket 16 has a shape adapted to the
configuration of coupled detection modules 2, and, as it is shown
in possible embodiment presented in FIG. 1 or FIG. 7, it has for
example a form of a ring, or has a shape close to regular hexagon,
as shown in possible embodiment in FIG. 5.
The detection modules 2 are entirely made of non-magnetic material
and each detection module 2 is equipped at each end with a liquid
marker 7. In this possible embodiment of the invention, the liquid
marker 7 is an ampule with an aqueous solution of a chemical
compound that shortens the longitudinal relaxation time of water.
For example, the chemical compound may be NiSO.sub.4 and
CuSO.sub.4. Liquid markers 7 give a signal in magnetic resonance
imaging, and are visible in an MRI image. This allows for
determination of spatial position of each detection module 2 of the
TOF-PET tomography insert 1 placed inside the tunnel of the MRI
scanner 20 using the magnetic resonance imaging technique.
The TOF-PET tomography insert is equipped with a liquid marker
device 8, as shown in FIG. 1. In this possible embodiment of the
invention, a liquid marker device 8 is located on a front face
surface of the TOF-PET tomography insert 1, which is perpendicular
to the plastic scintillator stripes 3, and has a form of an ampoule
with an aqueous solution of a chemical compound which shortens the
longitudinal relaxation time of water. For example, such a compound
may be NiSO.sub.4 or CuSO.sub.4. Liquid marker device 8 gives the
signal in magnetic resonance imaging and is visible on the MRI
image. This allows for a spatial positioning of the TOF-PET
tomography insert inside the MRI scanner 20, as well as
establishing the relation of the geometry and dimensions of the
TOF-PET tomography insert 1 and PET image with the MRI image.
The TOF-PET tomography insert 1 is equipped with electronic signal
processing unit, and with a computer having software for
controlling the signal processing electronics, and software for
reconstruction and image preservation similarly as in any TOF-PET
scanner. Signal processing electronics and a computer with the
aforementioned software operate independently of the MRI
measurement setup.
As shown in FIG. 1 the TOF-PET tomography insert 1 has a protective
layer 13 made of non-magnetic material, for protecting the
detection modules 2 from inside of the working space 14. The
protective layer 13 secures scintillator stripes 3 against
mechanical damage, for example by the patient 5. The protective
layer 3 does not disturb imaging system performance, which consists
of the TOF-PET tomography insert 1, and the MRI scanner 20.
The TOF-PET tomography insert 1 is equipped with a base 12 made of
non-magnetic material, as shown in FIG. 1. The base 12 of the
TOF-PET tomography insert 1 does not perturb imaging system
performance, which consists of the TOF-PET tomography insert 1 and
the MRI scanner 20. The base 12 provides stability to the
construction formed by the coupled detection modules 2, which is
placed on the sliding bed 24 of the MRI scanner 20, or when one
uses the TOF-PET tomography insert outside the MRI scanner as a
standalone device. The base 12 should be made of non-magnetic
materials, including plastic, that has sufficient strength to
support the weight up to several tens of kilograms. To the base 12,
brackets 16 are mounted which support the configuration of
detection modules 2 forming the TOF-PET tomography insert 1.
The TOF-PET tomography insert 1 is equipped with a triggering unit
15. It is a receiving coil, with a resonance frequency in the
vicinity of the resonance frequency of hydrogen atoms nuclei
(magnetic resonance pulse frequency). Starting the MRI study it
generates a voltage signal in the coil of the triggering unit 15,
which presence is recorded and determines the start of the PET
acquisition. Triggering unit 15 starts the process of PET imaging
simultaneously with the start of MRI imaging.
Using only non-magnetic components for the construction of the
TOF-PET tomography insert 1 provides that the homogeneity of the
MRI scanner 20 magnetic field in test volume remains unaffected.
For the same reason the parameters of electromagnetic fields
applied during the performance of the MRI scanner 20 do not change
with respect to the performance of the MRI scanner 20 as a
standalone device. The data acquisition of the TOF-PET tomography
insert 1 is performed by the computer system which is independent
of the MRI scanner 20. Time synchronization between the TOF-PET
tomography insert 1, and MRI scanner 20 does not require an
electrical connection between the devices. Spatial synchronization
of the MRI and PET images does not require changes in the software
of the MRI system, which functionality is usually limited by the
manufacturer. Interference in the MRI system software is usually
forbidden, beside the changes (to the extent permitted by the
manufacturer) of basic parameters of the imaging sequences, or
recording and processing of acquired images for further radiologic
interpretation purposes. The synchronization is performed by the
PET image reconstruction system relying on the MRI images, where
signals from liquid markers 7, placed at both ends of each
detection module 2, as well as from liquid marker device 8, are
present.
Location of the signals from liquid markers 7 and liquid marker
device 8 on the MRI images gives a possibility of imposing the PET
and MRI images of the investigated object avoiding the problems
related to images relative shifts in three spatial dimensions as
well as with their relative dimensional scaling.
The TOF-PET tomography insert, is a TOF-PET scanner, but designed
in the way that it can operate as a standalone device or within any
MRI scanner 20, inside the transmitting-receiving coils 22, being
an independent and non-interfering in MRI scanner 20 construction.
The TOF-PET tomography insert 1 does not interfere in the technical
parameters of the MRI scanner 20 and does not interfere in
operation of the MRI scanner 20. MRI scanner 20 operation does not
interfere with the operation of the TOF-PET tomography insert 1,
and does not interfere in the technical parameters of the TOF-PET
tomography insert 1. The modular design of the TOF-PET tomography
insert 1 enables to arrange the geometry of the detection modules 2
according to the size and shape of the transceiver coil 21, which
is built in the MRI scanner 20, in particular local
transmitter-receiver coil 22, which is not an integral part of the
MRI scanner 20, and is dedicated to the study of individual
patient's 5 body parts (head, arm, leg, for instance) or to the
geometry and dimensions of the investigated object. The latter
requires to combine the appropriate number of detection modules 2
of the appropriate shape and size. This can be done even
immediately prior to imaging.
The TOF-PET tomography insert 1 has an unique system for
positioning inside the MRI scanner 20, as well as the triggering
unit 15 to synchronize the PET and MRI acquisition timing. The
TOF-PET tomography insert 1 may be put inside the MRI scanner 20
diagnostic tunnel 23 to enable simultaneous PET and MRI imaging. At
the end of the combined imaging procedure, the TOF-PET tomography
insert 1 may be taken out from the MRI scanner 20 diagnostic tunnel
23. These operations may be performed in a short time. The TOF-PET
tomography insert 1 is a compact, lightweight device, which
handling shall not constitute a problem for the operating staff.
This solution is desired to be much cheaper than commercially
available TOF-PET scanners.
The greatest advantage of the invention is that it may be directly
used in any MRI scanner 20, which is currently held by the medical
units as hospitals, so that the MRI scanner 20 and the TOF-PET
tomography insert 1 introduced into the MRI scanner 20 diagnostic
tunnel 23 constitute a device for the simultaneous MRI and PET
imaging.
The invention is clearly not limited to the disclosed embodiments,
and there are various modifications within the framework of the
patent claims without departing from the essence of the
invention.
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